The Signal project doesn't want non-official clients to connect to their network. I doubt you'll get them to release an official client for your bespoke dumbphone OS, so I'm afraid you'll have to accept unstable hackery as a way to run signal.
You may be able to create your own dumbphone by flashing something like PostmarketOS to a compatible second hand phone combined with a custom Signal client. Just apk remove the browser and any other utilities you don't need and even the librem phone might be fast enough for your use case.
> The Signal project doesn't want non-official clients to connect to their network.
They don't encourage it but they don't ban it either. Non-official clients absolutely exist for the network, some of which use signald, a backend service and abstraction layer for the signal protocol which is neither unstable nor a hack:
They have shut down third party clients, and reserve the right to continue that. Both use f the name signal, and connecting to their backend without it being their official client are the reasons given, and those seem to apply to signald just as much.
Given that happened six years ago and multiple unofficial clients continue to exist without threat of ban, I'd suggest this one example cannot be extrapolated.
It is true that Whisper Systems runs the network and can gatekeep it as they see fit.
But your claim that Signal, as a matter of course, bans unofficial clients is objectively not true.
Moxie has been pretty consistent on this point. He even gave a talk at C3 a couple years ago that was basically an hour long explanation for why he continued to think this way and that he hadn't changed his mind at all. https://media.ccc.de/v/36c3-11086-the_ecosystem_is_moving
Additionally, they're more or less required to go after trademark violations if they get too big.
> He even gave a talk at C3 a couple years ago that was basically an hour long explanation for why he continued to think this way and that he hadn't changed his mind at all.
In that talk he explains why they don't decentralize their protocol or the ecosystem.
His concern is that a decentralized ecosystem means actively supporting third party implementations and having to achieve consensus when making changes, which slows down (or flat out stops) their ability to evolve the protocol and turn out new features.
That's a totally orthogonal issue to banning unofficial, unsupported clients.
> Additionally, they're more or less required to go after trademark violations if they get too big.
That's a trivial problem to solve: don't put Signal in your client name.
The unofficial clients are part of the ecosystem. Centralizing the ecosystem means centralizing the back ends and the clients.
It's not orthogonal at all, and he's talked at length about how he views every client connected to their servers as under his control, and his dislike for unofficial clients, and his willingness to squash them if they get too big.
Before signal he was head of security at Twitter which has a similar 'squash unofficial clients if they get too big' policy.
> That's a trivial problem to solve: don't put Signal in your client name.
Unless there’s an official statement about unofficial clients being allowed, then that single example can and must be extrapolated: it’s the only factual evidence.
Moxie and Signal didn't do anything other than asking LibreSignal politely to stop using their servers. They didn't "shut down" anything, and they have shown no interest in shutting down signal-cli/signald.
MobileCoin, the cryptocurrency that Signal incorporates and essentially sanctions, uses signald for their bot[0].
the Signal Matrix bridge has hundreds if not thousands of open source users, plus Element One and Beeper users, all using signald and not having any repercussions for years. The only 3rd party Signal client that's caught any flak from Signal that I'm aware of is LibreSignal.
Would the donor behind the Signal Foundation, Brian Acton, one of the WhatsApp founders who disagreed with the Mark Zuckerberg model of the internet, support the use of his donation to make threats or engage in legal proceedings against "non-official clients". Are there any statements from him about "non-official clients". Mike Benham ("Moxie Marlinspike") is no longer running "Signal Messenger LLC".1 Signal Foundation and its subsidiary Signal Messenger LLC appear to be the entities that control the Signal trademark. For example, the US service mark "Signal" is now registered to "Signal Technology Foundation", not "Whisper Systems LLC".
I wouldn't call it unstable hackery. There's a library called signal-cli that's being used to develop a native desktop app for signal (as opposed to the absolutely horrible electron web app available officially). The server software is open source already, so it isn't hard to develop a to spec working client that only spoofs identifiers to prevent detection.
You may be able to create your own dumbphone by flashing something like PostmarketOS to a compatible second hand phone combined with a custom Signal client. Just apk remove the browser and any other utilities you don't need and even the librem phone might be fast enough for your use case.